The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Appliances, such as washing machines, dishwashers and microwave ovens, generally include a timer to allow a user to select an appliance function, a program interval for the appliance function, and/or a desired operation cycle. A typical electromechanical timer for a washing machine generally includes a rotary knob for selecting a preferred washing cycle, a cam operatively connected to a plurality of switching arms for opening and closing various electrical circuits associated with the switching arms, and a motor for driving the cam. When a user pushes the control knob, the control knob can be rotated to a plurality of positions corresponding to a plurality of washing cycles or appliance functions, and the cam is rotated by the control knob to a proper start position. When the control knob is pulled out, the washing machine starts to run and the motor drives the cam so that the switch arms are raised or lowered for closing or opening the associated electrical circuits in accordance with a predefined pattern defined by the elevation of the cam surfaces.
In the typical electromechanical timer, the various electrical circuits associated with the various appliance functions are completely controlled by the predefined pattern on the cam surfaces. Therefore, designing or programming the cam is complex and a cam with a predefined pattern is only suitable for a washing cycle. When a new washing cycle is desired, redesigning the cam is necessary. Moreover, due to the complex nature of the cam designing and cam control, it is difficult to precisely control the various appliance functions. For example, it is difficult to use the cam to precisely control the temperature of water and the period of adding warm water without wasting energy. Therefore, the typical electromechanical timer does not meet the increasing demand for energy-saving operation of the appliance.
Electronic devices have been used to replace the cam for a more precise control and easy programming of various appliance functions. The ability of the electronic devices to precisely control the various appliance functions meets the need for energy saving. In addition, reprogramming the electronic devices is much easier and more cost effective than redesigning a cam when a new washing cycle is desired.
An electronic timer, however, can incorporate many costly relays in the various electric circuits and is thus more expensive than an electromechanical timer. Further, an electronic timer generally includes a plurality of touch pads for setting the various appliance functions, and increases the level of complexity to operate when compared to a rotary knob used in the electromechanical timer. The rotary knob provides a familiar tactile and visual feedback to consumers and operates in a manner instinctively known to consumers from years of use.